It has long been known for artificial teeth, in particular incisor teeth or canine teeth, to be built up from layers. In doing so, a cutting-edge material is built up such that it covers most of a dentine material, apart from the basal area of the dentine material. The dentine material can be joined to the cutting-edge material in any suitable way desired.
Thus, it is known from DE-A1 38 27 657, for example, to first build up a basic body of dentine material and then to injection-mold around the latter.
It is known, not only in plastic teeth, but also in ceramic teeth, to vary the layer thickness of the cutting-edge material in order to give an appearance resembling natural teeth. An example of this is the solution according to German specification 1 903 935.
The cutting-edge material is typically translucent, and the dentine material is somewhat opaque. It has also already been proposed, however, to increase the translucency of the dentine material. In this case, especially if a metal skeleton is used, a special opaquer is employed to veneer the metal skeleton. To provide the translucency, the cutting-edge material is often made quite thick. Although this gives the tooth the desired impression of translucency, it also gives the tooth a slightly “washed-out” look.
An improvement to these known solutions is known from DE 101 27 728. In the solution according to DE 101 27 728, the cutting-edge material is comparatively thin and has an uneven layer thickness. The uneven layer thickness is intended to improve the similarity to the natural tooth. However, this means that the tooth has a rather uneven effect specifically in the incisal area. The layer thickness should also not be chosen too small, in order to ensure that sprues that are used to produce the dentine material cannot be seen through the cutting-edge material. Such sprues are not very satisfactory from the technical point of view and also unsatisfactory from the esthetic point of view.
To improve the “technical” look of artificial teeth, attempts have therefore been made, in the recent years and decades, to improve the similarity to the natural appearance by using specific colorations. Mention may be made here of the known painting technique, which is still used regularly even today, even though it is very much dependent on the skill of the dental technician and is labor-intensive.
Moreover, it has also already been proposed to incorporate a color gradient within the layers. This solution, however, is extremely difficult to implement on account of the technical difficulties involved, especially since it is necessary to establish an exact reference point, which is a spatial one and is therefore difficult to define.
To remove plastic bodies from molds, it has become known to select the mold separation lines such that the fewest possible undercuts are present. Typically, the removal of mold halves with undercuts typically requires the provision of complicated slides, which also impair the precision. Also in light of these considerations, typical teeth, particularly plastic teeth, are generally produced free of undercuts and tapering obliquely toward the incisal side, the mold separation taking place at the “thickest” point of the tooth which, in the case of incisor teeth, may be arranged relatively near to the incisal area. This too has led to rather smooth and straight surfaces.